After being ordained in 1947 for the Archdiocese of Baltimore, Father Peterson served as a Sulpician until 1956.

While teaching at St. Charles College, a minor seminary in Catonsville, he finished his graduate work and was transferred to St. Joseph in Mountain View, Calif. and then St. Edwards in Seattle, Wash. Before returning to the diocese in 1956, to attend to his mother who was in poor health at the time, he acquired a doctorate in canon law.

He eventually resigned from the Sulpicians and became an associate pastor at St. Clement Mary Hofbauer, Rosedale; St. Ann, Baltimore and Our Lady of Good Counsel, Baltimore. While serving at Our Lady of Good Counsel he worked part time in the Matrimonial Tribunal. After leaving Our Lady of Good Counsel he was given a fulltime position at the Tribunal while he was in residence at St. Mary Star of the Sea, Baltimore and St. Brigid, Canton.

In 1968 he was appointed as pastor of St. Lawrence Martyr, Jessup, for three years as he continued his parttime duties at the Tribunal. He then became pastor of Holy Family, Randallstown, but was no longer involved with the Tribunal.

After two years Father Peterson was given permission to go to St. Elizabeth’s Hospital in Washington D.C., a federal psychiatric hospital. For 10 years, after an internship in clinical pastoral training, he was involved in pastoral care for patients suffering from mental illness, helped train others in clinical pastoral care and evaluated research papers by those who were attempting to qualify as clinical psychologists, among many other things.

In 1988 Archbishop William D. Borders gave Father Peterson retirement status but he has continued to stay active in his priestly duties.“Since that time I have redefined the word retirement,” he said with a laugh and recounted what the dean of The Catholic University of America, Washington, D.C., had said to him many years ago, “the priesthood is not a career it’s a way of life and you are priest 24 hours a day until the day you die.”

In 1993, Father Peterson was appointed spiritual director of the Reparation Society, which was founded by Father John Ryan, S.J. who wanted to promote awareness of Our Lady of Fatima’s prophecies and requests in different ways. After the death of Father Ryan, Anna Pertch became president of the Reparation Society until her death in 1996 when Father Peterson was elected to the position.

Father Peterson discovered a gold crown decorated with pearls, rubies and emeralds which was designed to fit perfectly atop the head of the Reparation Society’s Our Lady of Fatima statue. Father Ryan had placed the crown in a safe deposit box many years ago for safe keeping and never took it back out, recalled Father Peterson.